Diesel and gasoline engine vehicles use emission control devices to reduce emissions produced during combustion. The durability of an emission control device may depend upon a regeneration process, which may require increased exhaust gas temperature. For example, lean NOx traps and/or particulate filters may be at least partially regenerated during increased exhaust temperature conditions, along with specific exhaust air-fuel ratio conditions.
Certain changes in driving conditions during a regeneration of an emission control device may cause temperature excursions (e.g., beyond an upper temperature limit) which may degrade the performance of the emission control device. In particular, the frequency and/or amplitude of high temperature excursions may increase where excess reductants and excess oxygen are present in the exhaust. Such conditions may occur during short trips (key on/off cycles), motoring (mountain driving), and/or continued low speed operation, for example.
One approach to provide more controlled regeneration is described in the Japan Patent No. 4,086,319, where a particulate filter is regenerated manually. Specifically, when a driver turns on a regeneration switch, an exhaust throttle valve actuator throttles the exhaust and acceleration actuator increases fuel injection to increase engine speed and the exhaust temperature for re-combustion of particulates.
However, the inventors herein have recognized several disadvantages of the '319 approach. For example, raising engine speed alone may not generate temperature high enough for the regeneration of a particulate filter. Further, the use of an exhaust throttle may increase cost and may decrease peak torque.
Thus, the above issues may be addressed by a method of regeneration of an emission control device in a diesel engine of a vehicle having a wheel brake and a transmission. The method comprises receiving a regeneration request by an operator of the vehicle; activating the wheel brake; increasing engine torque; and regenerating the emission control device.
According to another approach, a method is provided for the regeneration of an emission control device in a diesel engine of a vehicle having a wheel brake and a transmission. The method comprises receiving a regeneration request by an operator of the vehicle; adjusting transmission operation; increasing engine torque; and regenerating the emission control device.
In this way, it is possible to utilize engine loading via the wheel brakes, thereby enabling increased engine loading during various engine operation conditions such as at idle state. Further, it is possible to generate engine loading greater than that caused by increased friction operating at higher engine speeds. Furthermore, such operation may be advantageously initiated by an operator so that vehicle braking (which may be automatically controlled) may be performed under expected conditions. Thus, exhaust temperature may be raised to a level required for the regeneration by increasing engine torque that can be counteracted by a load torque, such as a brake torque.
Similarly, transmission operation, such as gear state, may be adjusted to enable brake torque on the engine (e.g., via the wheel brakes) and thus enable increased engine loading to provide exhaust temperature sufficient for regeneration during stationary vehicle conditions. In one embodiment, the approach may be used to remove SOx in a lean NOx trap or particles from a particulate filter, thus multiple emission control devices may be regenerated, possible at the same time.